A typical motor-vehicle door latch is actuated by a handle which as described in German patent 3,030,519 of Keller has two main parts, a backing plate that lies against the inside surface of the outer door panel and a handle which lies outside the outer door panel and that engages at both ends through the panel. At one end the handle is coupled to the motor-vehicle door latch, normally via a locking mechanism that can block or uncouple the handle. At the opposite end the handle is mounted inside the door on a pivot formed by the backing plate.
While such a mechanism is fairly simple it constitutes a particularly easy point of attack for an unauthorized unlocking of the door. A would-be thief need merely pull the handle forcibly outward, typically with a pry bar, so that it can be removed completely from the door, leaving a hole through which access can be gained to the latch and look mechanism. A tool such as a screwdriver can be inserted into the thus created hole to actuate the latch and open the door.
German patent 3,238,964 of Grabner proposes a system wherein the handle is formed with a lobe that interfits with structure of the backing plate so that the two cannot be separated without destroying one or the other. While this arrangement is fairly effective, it is quite complex to manufacture and rather difficult to install in the vehicle.
Neither of these prior-art systems is integrated into an on-board motor-vehicle alarm system. Thus the would-be thief can work away at the latch and will not set the alarm off until he/she actually opens the door.